The term "cyclopentadiene" as used herein refers to the compound having the formula ##STR2##
The term "cyclopentadiene-type compounds" as used herein refers to compounds having the cyclopentadiene structure within their structure. Examples include unsubstituted cyclopentadiene, unsubstituted indene, unsubstituted fluorene, and substituted varieties of such compounds. Also included is tetrahydro indene.
Cyclopentadiene-type compounds have found a number of uses in the past. Some such compounds have been found particularly useful for preparing metallocene compounds. Recently, there have been publications which indicate that a wide range of alkyl bridged bis-cyclopentadienyl compounds are useful as ligands for preparing metallocenes which have utility as catalysts for the polymerization of olefins. Some examples of patents containing such broad disclosures include U.S. Pat. Nos. 4,808,561; 4,794,096; 4,892,851; 4,769,510, and 4,933,403, the disclosures of which are incorporated herein by reference.
While the patents contain broad general statements regarding the effectiveness of a broad genus of compounds, a careful review of the prior art reveals that those statements were based upon the results obtained with only a few of the compounds falling within the patents broad disclosures. Further, the patents do not contain teachings as to how one could make all the compounds which fall within their broad general disclosures. Routes for producing at least some of those compounds falling within the broad teachings of those patents are far from being obvious to one having routine ordinary skill in the art, particularly if one is looking for an economical process for obtaining relatively pure compounds. For example, the only actual example in the patent literature of a bridged cyclopentadienyl-type compound containing a fluorenyl radical appears to be the (cyclopentadienyl) (fluorenyl)-dimethyl methane referred to as isopropyl (cyclopentadienyl) fluorenyl in U.S. Pat. No. 4,892,851. That patent is not considered to disclose how one could make compounds in which a cyclopentadienyl and a fluorenyl radical were bridged by bridging groups other than dimethyl methane.
U.S. Pat. No. 3,426,069 discloses a method for making what is stated to be bis(9-fluorenyl) straight chain alkenes having a straight chain bridge of at least 2 carbon atoms by reacting fluorene with a diol in the presence of an alkali metal hydroxide. The process involves extreme reaction conditions and still provides a yield of only about 20% based on the moles of fluorene reacted.
One object of the present invention is to provide new methods for preparing certain cyclopentadiene-type compounds.
Another object is to provide methods which can provide increased yield of the desired cyclopentadiene-type compounds.
Another object is to provide methods which can produce cyclopentadienyl-type compounds that are more readily obtained in substantially pure form.
Still another object is to provide certain new cyclopentadienyl-type compounds.
Other aspects, objects, and advantages for the present invention in its various embodiments will become apparent to those skilled in the art from the disclosure which follows: